Specific Absorption Rate (SAR) is a measure of the rate at which energy is absorbed by the human body when exposed to Radio Frequency (RF) energy. SAR is defined as the power absorbed per mass of tissue and has units of watts per kilogram (W/kg) or milliwatts per gram (mW/g). SAR is usually averaged either over the whole body or over a small sample volume (typically 1 gram or 10 grams of tissue). The Federal Communications Commission (FCC) has adopted limits on SAR for cellular and wireless devices below which the level of exposure is considered safe. Currently, the FCC limit for exposure from such devices is 1.6 milliwatts per gram (1.6 mW/g). Manufacturers of cellular and wireless electronic devices face a difficult challenge in meeting the FCC limit for SAR while still providing sufficiently high RF transmission power to ensure an acceptable level of device performance.